system test configs are broken

Details

Description

system test suite has a set of default config values that are picked up from the testsuite/config directory. One can override the value of a config in the testcase_properties.json file. This is great, but the assumption is that the config property that is being overridden should also present in the testsuite/config/*.properties file.

Currently, there are a number of properties in KafkaConfig that are not in the testsuite/config/*.properties file. So the tests might intend to override some properties, but that will be ignored.

Let's either add all the configs in the testsuite/config/*.properties file or remove this depedency and override the property specified in testcase_properties.json.